Sunday, November 30, 2014

Geo 730: November 30, Day 699: Perched Water

Turning around to look at the outcrop across the road, we see the jointed lava flow overlain by rubbly lahar deposits. I (and others) have mentioned before that alders- the trees growing in a horizontal row across this cut- like to have their feet wet, and a tight cluster like that suggests a concentration of water. See comments 12 and 13 here, and my write up on the "Cheshire Cat outcrop," here, particularly clue #2. So that line of trees tells you that there's a bit more water in that portion of the cut than elsewhere, and that makes perfect sense. The lava, while jointed, is less permeable than the loose lahar deposits, so water tends to flow laterally along that contact until it reaches the surface, and signals its presence by supporting a stand of alders.

Photo unmodified. October 10, 2012. FlashEarth Location (possibly maybe).

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